This invention relates to foam blowing agent blends of trans-1,2-dichloro-ethylene (“Trans 12”) with one or more pentanes, and to polyol premixes and foam compositions containing such blends, more specifically to blends of Trans 12 with one or more of n-pentane (“n-C5”), i-pentane (“i-C5”) and cyclopentane (“c-C5”). The foam blowing agent blends are particularly useful for making closed cell polymer (insulation) foams having improved fire resistance, such as polystyrene, phenolic and polyurethane foams.
Chlorofluorocarbons (“CFCs”) had been used as blowing agents for rigid, closed cell insulation foams for many years because they offer outstanding fire resistance in addition to good thermal insulation. However, CFCs have been phased out because they are said to be detrimental to the ozone layer. Zero ozone depletion alternatives such as pentanes have been identified, but pentanes are highly flammable and their resulting foams suffer undesirable fire performance properties. It is increasingly difficult for pentane blown foams to meet stringent fire performance requirements, so that yet another alternative with better fire resistance performance is desirable.